#define _CRT_SECURE_NO_WARNINGS 1

#include <stdio.h>

int main()
{
    char ch = 0;
    scanf("%c", &ch);
    if (ch >= 'A' && ch <= 'Z' || ch >= 'a' && ch <= 'z')
    {
        printf("YES");
    }
    else
    {
        printf("NO");
    }
    return 0;
}